P9(4): remove local-core live-test trio — outbound speed test + egress probe, restart/stop xray endpoints

Per user decision 2026-10-21 (reverses the earlier keep call in
PANEL-LITE-SPEC.md, now amended): the lite panel never runs a local
core, so measuring/probing from the panel host is meaningless.

Backend:
- delete service/outbound probe implementation (probe_http.go and its
  tests) and the TestOutbound/TestOutbounds batch prober; outbound
  traffic accounting (AddTraffic/GetOutboundsTraffic/Reset) unchanged
- drop POST /panel/api/xray/testOutbound + testOutbounds routes and the
  outboundTestUrl setting (get/update plumbing removed; stored rows in
  existing DBs are inert)
- drop POST /panel/api/server/restartXrayService + stopXrayService
  routes/handlers and the node-sync allowlist entry; the service-level
  Stop/RestartXrayService stay for internal import/restore flows
- node-sync allowlist contract test updated to the new inventory

Frontend:
- remove test buttons/mode switch/test-all from outbounds tab, card
  list and table columns; delete TestResultPopover and CountryPill;
  drop the egress/country/latency columns fed by probe results
- remove outboundTestUrl state and save plumbing from useXraySetting
  and the Basics tab field; drop OutboundTestResult schemas
- delete the 15 now-dead i18n keys from all 13 locales (incl. the
  restart/stop keys orphaned since P6/P7 — i18n-dead-keys test green)
- tests: drop the test-URL hook test, re-probe the loopback index
  mapping through Move-to-top, regenerate API types (gen)

internal/web/service/setting.go

@@ -106,7 +106,6 @@ var defaultValueMap = map[string]string{
 	"nord":                       "",
 	"pia":                        "",
 	"restartXrayOnClientDisable": "true",
-	"xrayOutboundTestUrl":        "https://www.google.com/generate_204",
 	"panelOutbound":              "",
 	"devChannelEnable":           "false",
 
@@ -352,18 +351,6 @@ func (s *SettingService) GetXrayConfigTemplate() (string, error) {
 	return s.getString("xrayTemplateConfig")
 }
 
-func (s *SettingService) GetXrayOutboundTestUrl() (string, error) {
-	return s.getString("xrayOutboundTestUrl")
-}
-
-func (s *SettingService) SetXrayOutboundTestUrl(url string) error {
-	clean, err := SanitizeHTTPURL(url)
-	if err != nil {
-		return err
-	}
-	return s.setString("xrayOutboundTestUrl", clean)
-}
-
 func (s *SettingService) GetListen() (string, error) {
 	return s.getString("webListen")
 }